Shares in US biotech Dendreon increase after Congress members call for an investigation into an FDA decision not to approve the company's immunotherapy vaccine for prostate cancer, Provenge

US-based Dendreon has seen its share value increase after three members of US Congress called for an investigation of the FDA's decision not to approve the company's immunotherapy vaccine for prostate cancer, Provenge (sipuleucel-T).

Shares in the biotech closed up USD 1.34 (23.8 per cent) to reach USD 6.98 when congressmen Michael Michaud, Dan Burton and Tim Ryan asked the House Energy and Commerce Committee to conduct a hearing on whether conflicts of interest affected the FDA's May 2007 decision.

In a letter to congress, the three politicians wrote, "serious ethics rules were violated by two FDA advisory panel members".

The FDA has not yet replied to the letter.

In May 2007, the FDA requested more information before approving Provenge, much to the annoyance of prostate-cancer patients and shareholders who had expected a quick approval after a hearing in March.

McAdams Wright Ragen analysts say that it is unlikely that a congressional investigation will accelerate the approval of Provenge, because clinical trial results sought by the FDA could be available before the inquiry reaches any resolution.

The FDA's decision led to lawsuits against the regulatory agency itself and prompted activist rallies in Washington and Chicago.

Critics who sued the FDA claim that an agency official sabotaged Provenge's approval because he wanted to make his mark as the new chief of oncology drugs within the organisation. The lawsuit alleges he placed two advisers with conflicts of interest on the panel reviewing the drug.

The majority of the lawsuit claims were dismissed in late November 2007 by a federal judge, according to CareToLive, the organisation that filed the lawsuit. The group filed an appeal in early December.

Some industry watchers say that the Provenge data was not strong enough to guarantee the drug's approval.